1. Technical Field
The present invention generally relates to a method for the encapsulation and delivery of bioactive components using a protein to extract and retain the flavor. In particular, the water insoluble properties of a prolamin can be used to extract, concentrate and deliver the non-water components of an aqueous food derived from a natural source.
2. Description of Related Art
Flavors can be important in any food formula and can influence the finished product quality and cost. It is important to harness flavors and aromas to make products appealing to consumers for as long as possible after the product is initially produced. However, the complex systems associated with flavors are often difficult and expensive to control. For example many flavors contain top notes that are quite volatile, vaporizing at or below room temperature. These top notes are often what give foods their fresh flavors. Consequently, because aroma and flavorings are usually delicate and volatile, their retention remains an ongoing concern for food manufacturers. Manufacturing and storage processes, packaging materials and ingredients in foods often cause modifications in overall flavor by reducing aroma compound intensity or producing off-flavor components. In addition, once a product is on the store shelf, oxidation, hydrolysis, staling, and other processes may also cause it to lose its desired attributes and develop off-flavors.
To limit aroma degradation during processing and storage and retain aroma and flavor of a food product, it is beneficial to encapsulate the volatile flavor ingredients prior to use in foods or beverages. Encapsulation is the technique by which one material or a mixture of materials (known as active or core material) is coated with or entrapped within another material or system (referred to as shell, wall material, matrix, carrier or encapsulant). Different processes are used for encapsulation so as to impart some degree of protection against evaporation, reaction, or migration in a food. Encapsulation of flavors has been attempted and commercialized using many different methods, often dependent upon the end use of the product, the physical and chemical properties of the core material, the degree of stability required during storage and processing, the maximum obtainable flavor load, and the production cost. Further, the ratio of the core material flavor to wall material will affect the anti-oxidative stability of an encapsulated flavor.
Spray drying is a commercial encapsulation process often used in the food and pharmaceutical industries. The process involves the dispersion of the substance to be encapsulated in a carrier material, which is typically a modified starch, as a suspension in water to form a slurry. The slurry is then fed into a hot chamber, where it is atomized to form small droplets and dried to a powder. This technology produces a very fine powder. Table 1 outlines the advantages and disadvantages of the spray-drying technique.
TABLE 1Advantages and Disadvantages of Spray-Drying.AdvantagesDisadvantagesLow operating costProduce no uniform microcapsulesHigh quality of capsules in goodLimitation in the choice of wallyieldmaterialRapid solubility of the capsules(low viscosity at relatively highSmall sizeconcentrations)High stability capsulesProduce very fine powder whichneeds further processingNot good for heat-sensitive material
In particular, it should be noted that heat-sensitive materials such as the volatile components of flavorings are often lost or degraded during spray-draying. Often times, even trace components can have an important impact on the smell and/or taste of a flavor, and any loss of these volatiles can affect the authenticity of a flavor.
Table 2 illustrates several of the different major materials currently used with spray drying techniques and their desired characteristics for encapsulating flavors. The materials listed are not an exhaustive list. Many encapsulations are actually composite formulations of any or all of the compounds listed.
TABLE 2Wall materials typically used in flavor encapsulations.Wall MaterialCharacteristicsMaltodextrin (DE < 20)Film formingCorn syrup solid (DE > 20)Film forming, reductabilityModified starchVery good emulsifierGum ArabicEmulsifier, film formingModified celluloseFilm formingGelatinEmulsifier, film formingCyclodextrinEncapsulant, emulsifierLecithinEmulsifierWhey proteinGood emulsifierHydrogenated fatBarrier to oxygen and water
In recent years, there has been a trend towards clean label formulations and labels, or natural foods. Some consumers desire products free of preservatives and artificial ingredients and prefer to consume products developed with natural ingredients. Prolamins are an example of a potential replacement for artificial ingredients presently used in the art. Prolamins are a group of plant storage proteins, high in proline content and found in the seeds of cereal grains. They are characterized by their solubilities in aqueous alcohol and by the fact that upon hydrolysis they yield a relatively large amount of amide nitrogen and proline, a cyclic, nonpolar amino acid. Gliadin is a prolamin protein from wheat, hordein is a prolamin protein from barley, secalin is a prolamin protein from rye, and zein is a prolamin protein from the maize kernel or corn.
Zein is one of the few cereal proteins extracted in a relatively pure form and is a natural, biodegradable polymeric material. Zein is an odorless, amorphous powder rich in branched amino acids. It constitutes 44-79% of the corn endosperm protein, depending on the corn variety and separation method used. The only known function of zein in nature is to act as storage for nitrogen in the developing seed of the maize kernel. Unlike most other commercially available proteins, it has unique thermoplastic and hydrophobic properties. It has a unique ability to form odorless, tasteless, clear, tough films and fibers that are highly resistant to water and grease.
In light of the trend towards “clean label” foods and the complexities of flavorings, a need exists for a method of utilizing more natural compounds for encapsulating flavors to reduce or substantially eliminate artificial or modified ingredients. Moreover, there is a need for further methods that utilize natural proteins such as zein to protect sensitive materials such as flavors from degradation or loss. There is also a need for an encapsulation method that provides for the retention of costly or complicated flavoring ingredients without masking or dampening of flavoring, while providing high flavor loading and maintaining shelf-life. In addition, there is a need for methods of encapsulating well-liked natural flavors in a way that maintains and preserves substantially all its flavorants and tastants so as to produce authentic natural flavors. Such a method would preferably provide for the extraction, concentration and delivery of flavor in a suitable matrix within one simple and cost-effective process and substantially within one step. Finally, there is a need for methods capable of concentrating and encapsulating not only flavors, but also the other bioactive components of a food.